Move Device Sensors client files from Blink to //device/sensors client lib

Currently, several Device Sensors files are part of the WebKit public
API. These files define POD structs that the Device Sensors implementation
and its clients use to consistently interpret shared memory.

As part of servicificying Device Sensors and enabling it to be used
by clients other than Blink, this CL moves those files into the Device
Sensors client library. It also updates naming conventions etc. to match
their new location.

Once concern in making this move is that Blink's modules implementations
cannot in general depend on Chromium code due to performance concerns. In
this particular case, the dependence is both necessary (for the
interpretation of shared memory) and safe (since the structs are POD and
must remain so). To avoid unwanted dependencies creeping in in the future,
the moved files are isolated in their own target within
//device/sensors/public/cpp, with a clear explanation in the BUILD.gn file
of the constraints on this target.

BUG=612322
TBR=jam

Review-Url: https://codereview.chromium.org/2415083002
Cr-Commit-Position: refs/heads/master@{#458372}
50 files changed